The invention relates to an electron tube provided with a cathode structure for emitting electrons, which is arranged on a support.
The electron tube can be used as a display tube or a camera tube but may also be embodied so as to be used for electrolithographic applications or electron microscopy.
An electron tube of the above-mentioned type is shown in U.S. Pat. No. 5,444,328. In a so-called "cold cathode", a pn junction is operated in reverse bias in such a manner that avalanche multiplication of charge carriers occurs. In this process, electrons may receive sufficient energy to exceed the work function potential. The emission of the electrons is further enhanced by the presence of a work function potential-reducing material, in particular cesium.
The use of cesium as the work function potential-reducing material often causes problems. For example, cesium is sensitive to the presence (in the operating environment) of oxidizing gases (such as water vapor, oxygen, CO.sub.2). In addition, cesium has a high vapor pressure so that it vaporizes readily. Dissipation of the cathode causes the cesium to be lost as a result of an increase in temperature. In addition, ESD (Electron Stimulated Desorption) occurs; the electrons emitted by the cathode induce desorption of the cesium, in particular from slightly oxidized surfaces. This loss of cesium causes the electron-emission coefficient of the cathode to decrease during its life-time, resulting in a substantial reduction of said life-time.